Ceramic fuel cell plates are stacked together to make a fuel cell stack into which natural gas is feed, producing electric power, water vapor and CO2. Such systems can operate at 60% efficiency, twice that of conventional coal-fired power plants.

The Remarkably Efficient Natural Gas Fuel Cell Car

Three developments could make ceramic fuel cell electric cars more practical than plug-in models

The hydrogen initiative is stalled. The hydrogen fuel cell
cars work fine but no good solutions have been found to the problems of where to get the hydrogen, how to
deliver it and how to store it.95%< of our hydrogen is made from natural
gas, which is abundant on earth and already distributed at 1/3rd of the price
of gasoline. Three recent breakthroughs have made natural gas a very
interesting fuel:

Ceramic fuel cells that can make electricity from natural
gas at 60%
efficiency.

A glut of cheap natural gas caused by new shale drilling/extraction techniques.

The fuel cell breakthrough is particularly important because it
means a car can generate its own electricity more
efficiently than a massive power plant! Big plants typically average
30% efficiency, so a 60% NG fuel cell hybrid is twice as efficient as an electric vehicle charged from
the grid. That means half as much fuel is consumed.

Twice as efficient as an electric car is saying a lot because
electric cars are already
three times more efficient than
conventional cars. This is because internal combustion engines are less
than 30% efficient verses 90% for electric motors. Natural gas fuel cell cars
are thus about six times more
efficient than today’s cars.
Using 1/6th as much fuel means pollution
is also 1/6th . But NG is inherently very clean.
and has 30% lower carbon content and virtually no sulfur, mercury, volatiles,
and Nox so pollution is way less than 1/6th.

Since NG fuel cells have a warm up time, the hybrid
batteries must have enough capacity for all-electric operation until warm up is
complete. After warm up, the fuel cell keeps the batteries charged and the
batteries provide power for peak loads and acceleration and recapture energy on
braking. A Prius uses 16.8 kW for continuous 70 mph driving on a level
road. The fuel cell must be able to supply this much power for steady
driving.

Natural gas is already distributed by pipeline to homes all over
the US, so home refueling is possible. Compressed Natural Gas (CNG) is
already used to run five
million vehicles worldwide.
Pump prices for CNG are about one third of the price of gasoline in spite of the expensive ($350k),
3600 psi pumps and fittings currently used for delivery. The pipeline cost of
natural gas is only 1/4th of the cost of crude oil with the same energy content. If much
simpler, 500 psi Adsorbed
Natural Gas refueling is adopted, prices could be reduced even
further.. Cost per mile for a NG fuel cell hybrid would currently be only 1/18th of present cars but could be reduced even further with low
pressure ANG refueling!

ANG fuel tanks contain activated carbon “sponges” that adsorb 160
times their own volume of natural gas. They can be made from Corn
cobs , which have a network
of nanoscale passageways that remain after carbonization. One gram of
this material has as much adsorbing surface area as a football field. When
natural gas is adsorbed on a carbon surface it ceases to act like a gas. Dense
storage at low pressure makes it possible to hide the much smaller tank inside
the car's frame. Even if we kept the existing CNG high pressure storage, the
tripled efficiency would allow fuel cylinders only 1/3rd as large as present CNG tanks.

So an NG fuel cell hybrid is a lot like a Chevy Volt with a fuel
cell replacing the range extender (engine/generator) and a much smaller
battery. Its battery only needs to be large enough to run the car during
warm-up of the fuel cell, currently about 15 miles. The Chevy Volt's 40-mile
battery is rumored to cost $5000, so the NG car's 15-mile battery would
cost $3125 less. Incidentally, at these battery prices a 400-mile range pure
electric car would need $50,000
worth of batteries! Clearly, small batteries with range extenders are the
way to go until we have a significant battery breakthrough. Pure electrics have
other problems too: A 110v, 20A household plug can only supply 2.2 kW
which means that, unless you add 220v service, 10 hours of home charging will
only take you 10 x 2.2 x 4 mi/kW = 88 miles.

Natural gas today is primarily a non-renewable, fossil fuel. But
people have already begun selling renewable gas into the pipeline. Landfills,
manure piles and sewage plants that used to release significant amounts of
methane into the atmosphere are now selling it as green gas. Biomass< and
garbage can also be gasified to add to the supply. The energy balance of grass
biomethane production is 50%
better than annual crops now used.

Though the US power grid uses significant hydro power and other
renewables, CO2 emissions are still almost twice as much per kilowatt-hour as a
60% efficient NG fuel cell. In 2007 the US power grid emitted 605 grams/kWh. A NG fuel cell emits only 327 grams.
At 4mi/kWh that translates to about 151 grams per mile for a grid charged car
verses 82 for the NG fuel cell car.

Someday the grid could be cleaned up so that electric cars charged
from it are cleaner than NG fuel cell hybrids. EIA data makes it easy to track our progress
towards this goal: In 1996 we emitted 627 grams of CO2 per kWh and by 2007 this
was reduced to 605 grams. That’s a 2-gram per year decrease. If we continue at
that rate, it will take 139
years to equal what we can do
now with a NG fuel cell. Recent years show even less progress. There was no improvement between 2006 and 2007. Plugging into
the grid is, unfortunately, a bit like plugging into a lump of coal.

Infrastructure expansion also favors natural gas. Gas pipelines cost
half as much to build as ugly
overhead electric transmission lines of the same power capacity. Gas also has one fourth the
transmission loss of electricity and much cheaper energy storage. Depleted gas
fields and salt caverns are already storing 4.1
Tcf of gas in the US. At 60%
efficiency this could produce 1,970 gigawatt-hours of electricity. A very cheap
battery!

Fuel cell developers are in a race to commercialize suitable fuel
cells. The first products using NG fuel cells are home CHP electricity generators that use their
waste heat to make hot water. The fuel cells in these units produce only 2 kW
but they can startup from an idle state in 5
or 6 minutes. Scaling up to 15 kW and adapting to the tough environment of
a car could take years. Another company is developing a fuel cell range
extender that is fueled by methanol. Methanol has only half the energy density
of gasoline but, because of the high efficiency<, fuel tanks would still be smaller
than current gasoline tanks.

“Price at the pump” is the one thing that seems to get voters
excited. Reducing fuel cost/mile by a factor of 18 with a fuel that is 97% from North America while using corncobs should generate
some excitement. The hydrogen
initiative should be
immediately redirected to focus instead on a fuel that is plentifully
available, transportable and storable.

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